The hypobaric hypoxia environment impairs bone strength and quality in rats

Introduction: Several studies report that bone development and regeneration at high altitude are different from those at low altitude. However, the conclusions are inconsistent. This study was designed to elucidate the effects of a hypobaric hypoxia environment on bone strength and quality. Methods: A total of 8 twelve-week-old male Sprague-Dawley rats were housed in different environments: hypobaric hypoxic (HX, n=4) and normobaric normoxic (NX, n=4). All rats were euthanized for examination at 21 d of the experimental period. The body weights were registered; the haematological values were counted; and the femurs were dissected for micro-CT, histological observation, and biomechanical testing. Results: After the 21-d treatment, the variation of body weights and haematological values confirmed that the simulative hypobaric hypoxia environment was effective, and the rats in the HX group had physiologically adapted to it. The micro-CT realistic 3D images and the histological observation showed that the HX group exhibited less trabecular bone in the distal metaphysis of their femurs. A quantitative analysis of the microCT data further validated this observation; rats in the HX group had lower trabecular bone mineral density (BMD), bone volume (BV/TV), trabecular thickness (Tb. Th), and trabecular number (Tb. N) and higher bone surface density (BS/TV) and trabecular separation (Tb. Sp) in the distal metaphysis of their femurs. The biomechanical properties (maximum load, stiffness and Young’s modules) of the femoral diaphysis were impaired by the hypoxic environment. Conclusion: These findings reveal that the hypobaric hypoxia environment negatively influenced bone strength and quality in rats.